JPS6096533A - Preparation of quartz glass tube - Google Patents

Abstract

PURPOSE:To obtain a high-quality quartz glass tube inexpensively, by gelatinizing a silica sol-containing solution with rotating it in a rotator, followed by evaporation, drying, and sintering. CONSTITUTION:Fine powder of silicic acid or alkylsilicate is hydrolyzed. This sol solution 6 is packed into the proper tube 5, and the tube 5 is rotated, to give hollow gel. It is dried by evaporation, to give dried gel, which is sintered and made into glass. Quartz glass is obtained at low temperature by this method. A quartz glass tube having inner surface close to mirror surface and no foam left in the interior can be prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a quartz glass tube, and more specifically, to a bath vessel in which a bath liquid containing at least silicic acid fine powder or silica gel obtained by hydrolyzing alkyl silicate is rotated. Nito 9 relates to a method for producing a quartz glass tube, which is gelled while rotating, evaporated to dryness to form a dry gel, and vitrified by sintering the resulting hollow dry gel.

Looking at the recent progress in optical fiber technology, the speed with which it is progressing is astounding. Sooner or later, this technology will be used in the consumer field and become familiar to the general public. However, in that case, the cost of fiber is not an issue and must be low.

When manufacturing optical fibers, quartz glass tubes are used as cladding tubes and support tubes, but the outer diameter,
These conventional quartz glass tubes have the drawback of being very expensive because precision is required in terms of circular diameter, cross-sectional area, etc.

Therefore, an inexpensive manufacturing method is required. On the other hand, if inexpensive quartz glass tubes are manufactured, they will be used in physical and chemical instruments, furnace tubes, etc. due to their excellent characteristics, and are expected to have a great impact.

An object of the present invention is to provide a quartz glass tube that is inexpensive and of high quality.

The conventional manufacturing method for quartz glass tubes uses raw materials such as natural quartz.
The main method is bath melting at a high temperature of 00°C or higher, but in this case, there are problems such as the lack of materials that can withstand high temperatures, the intrusion of impurities, and the consumption of a large amount of energy, making it difficult to manufacture at a low cost.

The method of the present invention is an application of the sol-gel method, and 120
It has the characteristic of being able to produce quartz glass at low temperatures around 0°C. A method for producing quartz glass using the sol-gel method will be briefly described below.

First, a suitable alkyl silicate (Si(OR)4:
(R represents a suitable organic group) is hydrolyzed in water or aqueous alcohol. A catalyst such as hydrochloric acid may be used during hydrolysis. Depending on the case, a solution in which fine powder silica (Caposil, manufactured by Cabot Corporation; Aerosil, manufactured by Degussa Corporation) is dispersed may be used, or fine powder silica and the above-mentioned silica sol may be mixed.

After the silica sol is produced in this manner, it is dried to form a dry gel, which is then further dried, sintered, and vitrified.

The features of this method are as follows.

1. It is an energy-saving method because it can be made at low temperatures compared to the high-temperature bath melting method using quartz as a raw material. 2. Because it uses a low-viscosity solution as a starting material, high-quality glass without bubbles can be obtained. Can be done.

&　Quartz glass with good purity can be obtained.

Although the sol-gel method is thus an excellent method, it has conventionally been possible to obtain plate-shaped quartz glass, but it has been difficult to obtain tubular quartz glass.

The present invention is an epoch-making method that overturns this conventional concept. The outline is described below.

First, a suitable commercially available alkyl silicate, such as ethyl silicate, is added to a water bath solution containing (or not containing) alcohol (e.g., methanol, ethanol, etc.), (hydrochloric acid,
In addition to (may contain nitric acid, ammonia, etc. as a catalyst),
Stir and mix to perform hydrolysis.

After hydrolysis, this solution may be used in the next step, or the above-mentioned fine silica powder may be further dispersed in this solution before use.

Alternatively, a solution in which only fine silica powder is dispersed may be used.

The sol thus obtained is placed in an apparatus as shown in FIG. 1 and gelled while rotating to obtain a hollow gel.

To explain Figure 1 here, ■ is the motor for rotating the rotating body, ■ is the bearing, ■ is the rotating shaft, ■ is the plug,
(2) is a tubular body made of glass or plastic, which is filled with sol and rotates. ■ indicates the charged sol solution and the support stand, respectively.

In this way, the sol is placed in the device and rotated at an appropriate rotation speed for an appropriate period of time to form a gel, but if the rotation speed is slow, the liquid that has risen to the top may fall. It will not become a perfect circle.

Furthermore, if the gel is rotated too quickly, cracks will appear in the gel after gelation.

Incidentally, the time required for gelation can be adjusted depending on the person who adjusts PR, and can be set arbitrarily.

The above is the basic outline, but silica glass of various shapes can be obtained by changing the shape of the rotating body in various ways, by standing the device vertically, and by suppressing the number of rotations.

Also, if a hydrolyzate of other metal alkoxides is used,
Tubular glasses of various compositions can be obtained.

In the following Examples, aspects of the present invention will be explained in more detail.

Example 1 Purified commercially available ethylsilic-) (Si(00,)1
．． ) 4) 88ml of ethanol, 10-1 αQ2N hydrochloric acid solution 56trt, and 36ml of pure water were mixed to perform hydrolysis.

While applying ultrasound to this solution, 50 t of finely powdered silica (Aerosil OX-SO, manufactured by Degussa) was gradually added.

After the addition, ultrasound was applied for an additional 2 hours to increase the homogeneity of the solution. After applying ultrasound, 7.2 d of LIN ammonia solution was added to adjust the pH to around 5.

This adjusted solution was filled into a glass tube with an inner diameter of 21mm and a length of 200 knots, which was then incorporated into the apparatus shown in FIG. 1 and rotated at a rotational speed of 400 rpm for 40 minutes.

After the rotation, the glass tube was removed and a stopper with a hole of 4 mm in diameter was placed on both sides of the glass tube, and dried in a constant temperature bath at 60° C. for one week to obtain a dry gel. The size of the dried gel was 15 mm in outer diameter, 7 mm in inner diameter, and 135 mm in length.

Next, this dried gel was placed in a furnace and heat-treated according to the temperature program shown in FIG. 2 to form a quartz glass tube.

The quartz glass tube had an almost perfectly circular tube shape with an outer diameter of 11mm and an inner diameter of 5mm. In addition, although pockmarks were seen here and there on the outer surface, there were no bubbles on the inner surface and inside, which was very clean. In particular, the inner surface has a mirror surface, making it ideal for use as a support tube or clad tube.

The fact that it was made of quartz glass was confirmed by IR spectrophotometry, X-ray diffraction, specific gravity, hardness, etc.

Example 2 Ethyl silicate) 44.7jl', ethanol 6-1α
Hydrolysis of ethyl silicate was carried out by stirring and mixing 1N hydrochloric acid (46%) in a flask for 9.5 hours.

After hydrolysis, α1N ammonia solution was added to this mixture to adjust the pH to around 6, and the mixture was filled into a propylene container with an inner diameter of 20 mm.

Subsequently, in the same manner as in Example 1, a dry gel of a medium size was obtained. The obtained dried gel had an outer diameter of 12 mm and an inner diameter of 6 mm.

When this dried gel was heat-treated to 900° C. at a heating rate of 30° C./hour, a quartz glass tube with an outer diameter of 101 m and an inner diameter of 5 mm was obtained.

The quartz glass was confirmed in the same manner as in Example 1.

Example 3 After dispersing Aerosil 0X-50,409 in 10 rows of pure water, the pH-adjusted solution was charged into a glass tube in the same manner as in Example 1 and rotated until gelatinized.

The obtained gel is placed in a dryer and dried to form a dry gel.

This dry gel was placed in an oven and heated at a heating rate of 60°C/hour for 1 hour.
The temperature was raised to 450°C to vitrify it.

As described above, the manufacturing method of the present invention produces quartz glass at a very low temperature, the inner surface of the tube is close to a mirror surface, and no air bubbles remain inside. This is an excellent method for manufacturing quartz glass tubes.

If support tubes and cladding tubes can be supplied using this manufacturing method, optical fibers will be supplied at lower prices, and this will have a great effect on optical technology fields such as optical communications and local networks. is.

Furthermore, since the method of gelling while applying centrifugation has the effect of removing air bubbles, it can also be applied as a method of manufacturing high-quality photomask substrates for ICs.

For example, using a large rotating body and making a large quartz glass tube, I7I? ) It may be taken out and used as a photomask substrate, or the container contained in the sol may be swung in a large radius to form a gel, and then quartz glass may be formed by the method described above, and the quartz glass may be polished and used as a photomask substrate.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing the apparatus used in the method of manufacturing a quartz glass tube of the present invention. body, ■
indicate the sol and the support stand, respectively. FIG. 2 is a diagram showing a sintering temperature program. Applicant: Suwa Seikosha Co., Ltd. Patent Attorney: Tsutomu Mogami

Claims (1)

[Claims] A solution containing silica gel obtained by hydrolyzing a fine silicic acid powder or an alkyl silicate is evaporated to dryness to form a dry gel, and the resulting dry gel is sintered to obtain glass.Quartz glass #! In the production method, the bath solution is placed in a rotating body, gelled while being rotated, and then evaporated to dryness to form a dry gel. A manufacturing method for quartz glass tubes.